In the past, LED was used as signal(s), instead of being utilized as a lighting source (e.g. flashlights). Recent technological advancements enable LED (Light Emitting Diode) to have better reflection. In general, LED (light emitting device) uses reflection to guide light into a direction. The reflection of light is made by the surrounding/cover material to push light in certain direction(s). The quality of the reflection would be dependent on the shape of the surrounding. Such surrounding is collective referred as reflection unit.
Today, LED and the reflection surrounding (reflection unit) can be made separately or together. The reflection unit is generally made of plastic material. To achieve reflection capability, the unit is either formed by mixing TiO2 powder or other power with reflective property as such powders maintain certain reflective qualities or the reflection unit made of plastic material is coated with metal thin film such as aluminum and silver thin film. The layers may be as thin as several atoms and the thickness is generally less than one micron. It is well known in the art that such aluminum and silver thin film generate the most efficient reflection power.
There are two processes present in which one can use to plate the reflection unit. One is coating by electrical plating and the other is coating by vacuum coating. Electrical plating is not desirable in that the liquid is likely to sip into the crevice of the cover. This is true because in electrical plating, one will need to have all the crevices covered, and it is often difficult to do so. Therefore, vacuum coating process is preferred over electrical plating.
Specifically, vacuum coating is a process used to create a thin layer of a substance on a solid object. The object is placed into a vacuum chamber and a small amount of the coating material is vaporized into the chamber. The molecules or atoms of vapor condense onto the solid object, forming a uniform coating of controllable thickness.
Nevertheless, this vacuum coating process, especially as used in the context of coating the LED reflection unit, is in need of improvement. Specifically, in order to plate the area that needs to be not coated with metal thin film (non-coating area) in a vacuum plating process, one would need to cover the area that does not need to be coated. Thus, the quality of the cover plating or shield and how it is secured over the non-intended coating area will determine the quality of the coating.
Traditionally, the cover plate (shield) is held over the non-coating area by pressing the cover plate (shield) over the non-coating area with an external application. This method is not desirable. Specifically, this use of external application such as clip to secure the cover plate (shield) is also not desirable because such external application will have to be designed to avoid blocking the intended coating area as metal thin film deposes over the intended coating area and clip may inadvertently block the intended coating area. Further, because the size of the cover plate is now becoming increasingly small, the strength of the clips would need to be uniform or else the structure of the cover plate will be distorted.
As a result, it is desired that a method of vacuum deposition is available where cover plate (shield) can be held in place during vacuum deposition process without the presence of clips or clamps. Specifically, it is left to desire an improved method of vacuum deposition for coating the reflection unit of a light emitting diode (LED) chip substrate where the cover plate (shield) can be held in during vacuum deposition process without the presence of clips or clamps.